Recipe for the synthesis of metastable structures using topologically assembled precursors

Abstract

Methods of planning and executing the synthesis of metastable materials are provided. Topologically assembled precursors having potential energy surfaces in which the volumes of potential wells of certain local minima are increased are created in silico. The precursor molecules are used to synthesize, e.g. two-dimensional metastable carbon materials such as penta-graphene comprised entirely of pentagons, O-graphene comprised of five- and eight-membered rings, and R-graphene comprised of four-, six- and eight-membered rings.

Description

STATEMENT OF FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT[0001]This invention was made with government support under grant number DE-FG02-96ER45579 awarded by the United States Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering; and under grant number DE-AC02-05CH11231 awarded by the Office of Science of the United States Department of Energy. The United States government has certain rights in the invention.BACKGROUND OF THE INVENTIONField of the Invention[0002]The invention generally relates to the synthesis of metastable structures. In particular, the invention provides methods of selecting precursors with a high probability of forming the metastable structures, and methods of synthesizing the metastable structures using the selected precursors in modeling as well as in experiments.Description of Related Art[0003]Metastable structures provide us with a diversity of electronic and mechanical properties which, in many cases, are mor...

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Benefits of technology

[0007]Metastable structures of matter often possess properties superior to those of their ground state, e.g. diamond vs. graphite. Yet, in practice, many predicted metastable structures are dismissed as hard-to-realize as their corresponding local minima in the potential energy surface are either too shallow or too narrow or both. This disclosure provides methods that can enhance the realizability of targeted metastable structures deliberately and directly guide the experimental synthesis, as follows: First, a molecular precursor is identified according to its resemblance to the atomic, structural and local symmetry of the repeat unit of the targeted metastable structure; Second, different topological assemblies are achieved by confining the precursor units into a constrained superlattice with controlled overall orientation to induce connectivity between certain atomic nodes of the neighboring units; and Third, all the initial assemblies of the precursors are relaxed to their near energy critical point using density functional theory (DFT). The realizability of a structure is measured according to its frequency of occurrence in the relaxed Topologically Assembled Precursors (TAP). Thus, potential energy surfaces are created by design, in silico, in which the volumes of the potential wells of the metastable structures are increased, while suppressing the accessibility of structures of the ground state. The methods are applied to identify suitable precursors that can be used to synthesize high-energy metastable structures with exotic properties, such as 2D carbon allotropes, including penta-graphene comprised entirely of pentagons, O-graphene comprised of five- and eight-membered rings and R-graphene comprised of four-, six- and eight-membered rings. Crystalline solid materials prepared by these methods are also encompassed.

[0008]It is an object of this invention to provide a method of synthesizing a metastable crystalline material from a precursor comprising I) selecting the precursor by: i) identifying potential precursors, wherein the potential precursors are identified by—determining the number of atoms in a building block of the metastable crystalline material; —determining the types of bonds between the atoms in the building block; —selecting, from a molecular database, potential precursors having a) the same type of atoms as the builiding block, b) the same number of atoms as the builiding block, c) at least one bond of a type that is the same as at least one bond in the building block; —aligning the potential precursors; —selecting, as candidate precursors, potential precursors in which bonding between atoms of aligned neighboring potential precursors can occur; ii) for each selected candidate precursor, generating a set of different topologically aligned precursors (TAP); iii) geometrically and ionically relaxing each TAP to a closest critical point of the potential energy surfaces (PES); iv) calculating the frequency of occurrence of the metastable crystalline material within relaxed TAP; v) selecting at least one candidate precursor to be used as a precursor to synthesize the metastable crystalline material, wherein a frequency of occurrence of the at least one metastable crystalline material in the relaxed TAP of that candidate precursor is at least 2 times a frequency of occurrence of energetically similar metastable crystalline structures, and / or the ground-state of the metastable crystalline structure; and II) reacting the precursor to form the metastable crystalline material. In some aspects, the metastable crystalline material is a two dimensional (2D) or three dimensional (3D) metastable crystalline material, or an allotrope thereof. In some aspects, the metastable crystalline material comprises one or more of carbon, boron, nitrogen, phosphorus, silicon or a metal. In other aspects, the metastable crystalline material is a 2D carbon allotrope. In further aspects, the 2D carbon allotrope is penta-graphene, O-graphene or R-graphene. In some aspects, the step of geometrically and ionically relaxing is performed using density functional theory (DFT). In other aspects, the step of geometrically and ionically relaxing is performed while suppressing accessibility of the ground state and other isomers. In further aspects, each TAP is formed by contraining, within a superlattice, multiple copies of one candidate precursor. In additional aspects, each copy of the candidate precursor within the superlattice has the same fixed orientational configuration. In other aspects, the frequency of occurrence is at least twice the frequency of occurrence of energetically nearest neighbor structures and / or the ground-state structure. In further aspects, the frequency of occurrence is at least one order of magnitude higher than the frequency of occurrence of energetically nearest neighbor structures and / or the ground-state structure. In further aspects, the step of selecting comprises selecting potential precursors having at least one of: the same type of atoms as the building block of the metastable crystalline material, the same number of atoms as the building block of the metastable crystalline material, the same atomic orbitals as the building block of the metastable crystalline material, and the same size as the building block of the metastable crystalline material. In some aspects, the metastable crystalline material is pentagraphene and the precursor that is selected is 3,3-dimethyl-1-butene.

Problems solved by technology

Yet, in practice, many predicted metastable structures are dismissed as hard-to-realize as their corresponding local minima in the potential energy surface are either too shallow or too narrow or both.

Thus, potential energy surfaces are created by design, in silico, in which the volumes of the potential wells of the metastable structures are increased, while suppressing the accessibility of structures of the ground state.

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